Crimping synthetic thermoplastic yarns



y 1965 D. ca. JENKINS ETAL 3,196,602

GRIMPING SYNTHETIC THERMOPLASTIC YARNS Original Filed May 11, 1962 2Sheets-Sheet 1 9 Izqentora fl/u aa/ 414 14 4 M Attorney.

July 27, 1965 D. s. JENKINS ETAL 3,

CRIMPING SYNTHETIC THERMOPLASTIC YARNS Original Filed May 11, 1962 2Sheets-Sheet 2 p I gnugnjo s United States Patent 3,106,602 CRIMPINGSYNTHETIC THERMOPLASTIC YARNS Donald Glyn Jenkins, Ahersychan,Pontypool, and Brian Edward Clapson, Cwmbran, England, assignors toBritish Nylon Spinners Limited, Pontypool, England Qriginal applicationMay 11, 1962, Ser. No. 194,108. Divided and this application Sept. 6,1%3, Ser. No. 311,275 Claims priority, application Great Britain, May19, 1961, 18,251/61 7 Claims. (Cl. 57-157) This application is adivision of our copending application, Serial No. 194,108, filed May 11,1962, now abandoned.

The present invention concerns improvements in or relating to crimpingsynthetic thermo-pastic yarns, and to crimped yarns of syntehticthermo-plastic materials.

Continuous filaments of the various man-made varieties, such as those ofnylon, are produced in substanially smooth straight condition; and theymay be, and often are, used in the construction of fabrics in thatcondition, usually after having been twisted together as multifilamentyarns.

It is sometimes desirable, however, that such yarns should be given acrimped configuration, in order that the handleof fabrics madetherein-om should not be so smooth as is normally the case, and in orderthat these fabrics should be moreb ulky, or fuller, than fabrics madefrom the ordinary yarns, and that their covering power should begreater. Also, crimping of the yarns can introduce added stretchabilitythereto, if desired.

At the present time, a considerable number of processes for impartingcrimp to normally smooth straight continuous filament yarns are knownand practised. Some of these processes depend on twisting anduntwisting, some on bending a yarn around a sharp edge, and others oncompressing continuous lengths of yarn in a chamber so that the yarnassumes a zig-zag formation. In the case of the synthetic thermoplasticmultifilament yarns, such as those of nylon and Terylene (RegisteredTrademark), heat is applied in all these processes prior to orconcurrently with the application of the deforming force, so that theyarns are in a plastic condition at some period whilst the deformingforce is being applied.

We have now found that such synthetic thermoplastic multifilament yarnscan very simply be crimped at a high rate of production if they aresqueezed between the nip of two co-acting rollers, whilst the yarns aretwisted to a low degree and are at an elevated temperature, i.e. 100 C.or above, and provided that the conditions of the process are as definedhereinafter, and that the yarns are subsequently tensioned and some orall of the twist in them removed or even some small amount of residualtwist in the reverse sense imparted. The invention, therefore, comprisesa process for crimping a synthetic thermoplastic multifilament yarnwherein said yarn is squeezed between the nip of two hard,smooth-surfaced rollers, at least one of which is driven, whilst theyarn is in a lowtwisted state and at an elevated temperature i.e. aboveabout 100 C., and the yarn is then back-twisted.

The invention also comprises a crimped multifilament yarn of syntheticthermoplastic material wherein the crimp of the filaments is of aregular zig-zag nature having rounded apices, said crimp being planarover short lengths, with adjacent short lengths difiering in respect oftheir planar orientation. Such a crimped yarn is essentially free fromtorque and has a relatively low extensibility.

The amount of low twist in the supply yarn will be selected mainly oneconomic grounds, but it will depend 3,195,602 Patented July 27, 1965 onthe denier and on the denier-per-filament of the yarn, and it may be ofthe order of 4 turns per inch. The yarn may be pre-heated by dry heat,e.g. in the form of contact, radiation or hot air heating, and thetemperature to which the yarn may be heated may be within the rangebetween C. and a temperature 300 C. below the melting point of thethermoplastic material concerned.

The rollers, which may be mounted as in a mangle one on top of the otherwith their axis horizontal or which may be mounted side-by-side withtheir axis in the horizontal or the vertical plane, should be made of,or at least have a surface composed of, a smooth hard material, such asbrass. It is not necessary that the mating surfaces of the rollersshould actually be polished, however; and a slightly matt surface may besuitable. It is not absolutely essential that the surface material ofthe two rollers should be identical; but one roller should not have asurface which is significantly more resiliently compressible than theother. In general, it may be said that the surfaces of the rollersshould be of material which, for a given stress, is harder than thematerial of the yarn.

The diameter of the rollers is not critical, although it will have someelfect on the crimp produced. For instance, rollers of 1 inch diameterhave proved satisfactory, but larger or smaller diameter rollers thanthis may be used. Normally, the two rollers will be of similar diameter,and both will be driven.

The force to be applied to press the rollers together to squeeze theyarn therebetween will depend on the ma terial of the yarn to becrimped, and on the diameter and width of the rollers; and the value tobe selected will involve a compromise between the degree of crimpdesired and the tenacity of the crimped yarn that is required at anygiven twist value.

The ettects of the amount of low twist in the supply yarn, and of theload applied to the nip-rollers, are demonstrated in the followingTables 1 and 2. Table 1 shows the effect of varying twist with aconstant load; and Table 2 shows the effect of varying load with aconstant twist. In both cases the yarn is 950 denier/ 68 filament yarnof polyhexamethylene adipamide.

TABLE 1 Effect of varying twist with constant load of 164 lbs.

Crimp Brealn'ng Twist, turns per inch Frequency, load in Remarks onrimps grams per Crimp per inch denier 1 03 No crimp. 2 3.18 Poor crimp.7 3.15 Good crimp. l0 3. 04 Very good crimp.

TABLE 2 Eflect of varying load with constant twist of 4 turns per inchCrimp Breaking Load in 1b. frequency load in Remarks on Remarks on incrimps grams per Crimp Tenacity per inch denier 5% 3.42 Poor erimp Goodtenacity.

7 3. 30 Fair crimp. Do. 7 3.15 Good crimp Fair tenacity. 7 2.80 do Poortenacity. 7% 1.05 do Useless tenacity.

The crimp produced in the process is not apparent on egress of the yarnfrom the rollers; and it a concurrent post-setting treatment is applied,as by heating the yarn to an elevated temperature for a short period,the yarn will be set in the flat ribbon form which it is in on emergence from the rollers and this will lead to an enhanced crimp aftersome or all of the twist has been removed. Thus, a concurrent settingtreatment after crimping is preferred, and can conveniently be carriedout on the yarn while it is passing from the rollers to a wind-upmechanism. In the case of nylon yarns, for instance, this post-settingmay be accomplished by passing them through a radiant heater or incontact with a heated metal plate, and the same heating device may beemployed for both pre -heating and post-setting. The yarn should then betensioned and all, or most, of the twist removed. This can convenientlybe achieved at the time of wind-up by the use of a ring-spindle wind-up.It is possible, however, for the post-setting treatment to be carriedout on the yarns after they have been tensioned and de-twisted, ratherthan before. In that case, post-setting may be performed whilst theyarns are in hanks or whilst they are loosely wound in a soft package;and steam is then the preferred setting agent.

The rollers may be cold, or they may be at an elevated temperaturecompared with the room temperature.

In a convenient embodiment of the process of the invention,rnultifilament yarn of e.g. polyhexamethylene adipamide having a lowdegree of twist is withdrawn at e.g. 200 feet/minute, from a cheese-typesupply package by a pairof brass nip-rollers, both of which are drivenand through whose nip the yarn is passed after having passed in contactwith a metal strip heater to raise its temperature to, e.g. 120 C., andthe yarn is then passed through a guide to a ring-spindle wind-up whichremoves all, or substantially all, of the twist. The tension in theyarn, either before or after the nip-rollers, should not exceed morethan about 0.4 gram per denier. The total load on the rollers forcingthem together'may be of the order of /2 lb. per denier, but therelationship between load and denier is not linear.-

In such an embodiment of the process, the yarn may be of a wide range ofdeniers, e.g. from 70 to 950, and the denier per filament may be from 1to 15, for instance. In general terms, the finer the denier perfilament, the less amount of twist need be present in the yarn: forinstance, about 2 turns per inch only will sufiice for a 70 denier/75filament polyhexamethylene adipamide yarn. It is advantageous to use ayarn having low molecular orientation; and if the supply yarn isactually undrawn, suflicient drawing (orientation) can be arranged totake place at the nip of the rollers for most textile purposes.

Such an embodiment of the process of the invention is illustrated in theaccompanying drawings, in which:

FIGURE 1 is a diagrammatic representation of the threadline of suchembodiment; 7

FIGURE 2 is a perspective side view of a modified form of a rollerarrangement for use in such embodiment; and 7 FIGURE 3 is a side view,on an enlarged scale, of a length of yarn produced by the apparatus ofFIGURES l and 2.

In PEGURE 1, yarn 1 is shown being withdrawn over the top end of yarnsupply package 3, through guide 5 and thence around tensioner 7 whichimparts to it a substantially constant tension for the subsequent heattreatment. Such takes place by contact of the yarn with the curvedsurface of electrical heater plate 9, the tempera: ture of which isautomatically maintained constant by controller 11. The yarn whilst atthe required elevated temperature is squeezed between nip-rollers 15 ofthe roller assembly 13, both rollers being driven by means not shown inthe figure. The loading of top roller is effected by the presslfi'.After emerging from the nip of the rollers, the yarn, which will be insubstantially fiat ribbon form, is led through a guide 1?, thencedownwardly to balloon guide 21 of the ring-spindle wind-up.

4 In the balloon, the yarn is tensioned and de-twisted; and finally itis wound into package 23 rotated on its spindle by spindle-whorl 25, theyarn passing through traveller 29 which rotates around the verticallyrecipro cating ring 31.

Another method of loading the top roller of a pair of nip-rollers isshown in perspective in FIGURE 2. Rollers 35 and 37 are mounted oneabove the other in mounting 33. The axle of the top roller 37 is urgeddownwardly by hearing blocks, one of which is shown by reference numeral39. The load to be applied to these blocks is conveniently provided by abalanced tray arrangement, which comprises a tray mounted at the end oflong arms 43 and adapted to carry the required small weight 47, whichtray (when unweighted) is balanced by counterweight 4-9 on the otherside of pivotal points 51. The eifective load applied by the arms 43 tobifurcated rods 41, and thence to blocks 3% is many times the weight 47owing to the length of the arms 43 and to the closeness of the rods 41to the pivotal point of the system. Hook 53, which is one of a pair, isfor holding top roller 37 in place when the lower roller is removed.Again, both rollers are driven in this case also, but for simplicity thedriving means have not been shown.

Referring to FIGURE 3 there is shown, on an enlarged scale, a length ofyarn 1 after it has been crimped by the method of the present invention.The crimp in the yarn is of a regular zig-z'ag nature having roundedapices 55. The crimps'are planar over short lengths, with adjacent shortlengths 57 differing in respect of their planar orientation.

The invention will now be further illustrated by the following examples,which show the conditions for crimping a number of different yarns ofpolyhexamethylene adipamide.

EXAMPLE 1 950 denier/68 filament drawn yarn of polyhexamethyleneadipamide was twisted to 4 turns per inch. Such twisted yarn was used asthe supply yarn for crimping, and was withdrawn from itspackage at 150feet per minute at a tension of grams. The yarn was heated to atemperature within the range 180-200 C., and whilst at that temperatureit was squeezed between the nip-rollers, with a load thereon of 164 lb.The yarn emerged from the nip as a fiat ribbon, the filaments beinglightly stuck together and slightly deformed in cross-section. Whentensioned and dc-twisted to zero turns per inch the crimp was produced,the frequency in each filament thereof being about 7 crimps per inch.

The denier or" the crimped yarn was 1200 at wind-up; and the crimp ofthe filaments was of a regular zig-zag nature, the apiees, or knees, ofthe crirnps being rounded rather than saw-tooth (as in stufifenboxcrimped yarn), and the crimp-s lying in one plane over short lengths ofyarn but such planes alternating in their orientation. The crimped yarnwas of low extensibility and was essentially non-torque; and as such, itwas sutiable for knitting, weaving or for use in the pile of carpets.

EXAMPLE 2 70 denier/ filament drawn yarn of polyhexamethylene adipamidewas twisted to 2 /2 turns per inch. Such twisted yarn was used as thesupply yarn for crimping, and was withdrawn from its package at feet perminute at a tension of 3 grams. The yarn was heated to a temperaturewithin the range 2GG C., and whilst at that temperature it was squeezedbetween the nip-rollers with a load thereon of 128 lb. After tensioningand de-twisting, the yarn was crimped, each filament thereof containingsome 24 crimps per inch. The crimp was of the same essential nature asthat of the yarn of Example 1.

EXAMPLE 3 840 denier/140 filament undrawn yarn of polyhexamethyleneadiparnide was twisted to 4 turns per inch. Such twisted, undrawn yarnwas used as the supply yarn for crimping, and was withdrawn from itssupply package, and tensioned by the tensioning device to 300 gramstension, by the nip-rollers which were rotating at a surface speed of150 feet per minute. Before entering the nip of the nip-rollers, theyarn was heated to a temperature within the range 180-200 C. The loadapplied to the nip-rollers was 98 lb. The resultant yarn, afterde-twisting to zero turns per inch, was a crimped yarn of loworientation, drawing to a ratio of 2121 having occurred at thenip-rollers. The filaments of the yarn contained 20 crimps per inch; andthe crimp was of the same essential nature as that of the yarn ofExample 1.

Instead of a single supply package and single wind-up, a plurality ofsupply packages may feed the one pair of nip-rollers, and the yarnscrimped thereby be wound up either separately or together on onepackage. Instead of winding-up the crimped yarn on a bobbin, it may becoiled within a container. After wind-up, three or more such yarns maybe plied, e.g. some 2 or 3 turns per inch in the direction opposite tothe original twist in the singles yarns. Such plied yarns may then behankdyed and used for the pile of tufted carpet. The filamentscomprising the multifilament supply yarn may be other than circular incross-section; and, after being squeezed by the rollers, thecross-section of originally circular cross-section filaments is likelyto be deformed.

The process of the invention may be utilized to crimp all syntheticthermoplastic continuous filament yarns, including all nylons, Terylene(Registered Trademark) polyester fibre, Acrilan (Registered Trademark)polyacrylonitrile fibre, isotactic polypropylene and linearpolyethylene. The conditions of the process and the nature of the crimpimparted will naturally differ as between the various kinds of fibres;but useful results are obtainable in all cases.

What we claim is:

1. A process for crimping a synthetic thermoplastic multifilament yarnconsisting of the steps of:

(a) imparting a low degree of twist to said yarn;

(b) heating said twisted yarn to a temperature of at least C. but notgreater than 30 C. below the melting point of the material of the yarnwhilst the yarn is under tension;

(0) squeezing the twisted yarn between the surfaces of a pair of drivennip-rollers whilst it is at the said temperature; and

(d) back-twisting the yarn.

2. A process according to claim 1 in which the yarn is initiallyundrawn.

3. A process according to claim 1 in which the yarn is ofpolyhexamethylene adipamide and is heated to between -200 C.

4. A process according to claim 1 in which the backtwisted yarn isfurther heated whilst under low or zero tension.

5. A process according to claim 1 in which the surface, at least, ofeach of the rollers is composed of a material which, for a given stress,is harder than the material of the yarn.

6. A process according to claim 1 in which said low degree of twist isimparted by twisting the yarn up to about five turns per inch.

7. A crimped multifilament yarn of synthetic thermoplastic material madeby the process of claim 1.

References Cited by the Examiner UNITED STATES PATENTS 2,089,193 8/37Dreyfus 2872 2,451,919 10/48 Clarkson 2872 2,818,630 1/58 Le Boeuf 28722,917,779 12/59 Kurzke et a1. 2872 2,938,258 5/60 Starkie 2872 2,972,7952/ 61 Backer et al. 19-66 3,001,355 9/61 Evans 57-34 3,052,009 9/62Epstein et al. 2872 MERVIN STEIN, Primary Examiner.

1. A PROCESS FOR CRIMPING A SYNTHETIC THERMOPLASTIC MULTIFILAMENT YARNCONSISTING OF THE STEPS OF: (A) IMPARTING A LOW DEGREE OF TWIST TO SAIDYARN; (B) HEATING SAID TWISTED YARN TO A TEMPERATURE OF AT LEAST 100*C.BUT NOT GREATER THAN 30*C. BELOW THE MELTING POINT OF THE MATERIAL OFTHE YARN WHILST THE YARN IS UNDER TENSION; (C) SQUEEZING THE TWISTEDYARN BETWEEN THE SURFACES OF A PAIR OF DRIVEN NIP-ROLLERS WHILST IT ISAT THE SAID TEMPERATURE; AND (D) BACK-TWISTING THE YARN.
 7. A CRIMPEDMULTIFILAMENT YARN OF SYNTHETIC THERMOPLASTIC MATERIAL MADE BY THEPROCESS OF CLAIM 1.